1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to an apparatus for simplifying an input unit of integrated circuit.
2. Discussion of the Related Art
Conventionally, liquid crystal displays (LCDs) display pictures using an electric field to control light transmissivity characteristics of a liquid crystal material found within the display. Liquid crystal displays include a liquid crystal panel with liquid crystal cells arranged in an active matrix pattern and a driving circuit for driving the liquid crystal panel.
Gate lines and data lines are arranged on the liquid crystal panel in such a manner as to cross with each other. The liquid crystal cells are positioned at crossings of the gate lines and the data lines. The liquid crystal panel further includes a common electrode and a plurality of pixel electrodes for applying the electric field to each of the liquid crystal cells. Each of the pixel electrodes is connected to any one of the data lines through source and drain terminals of a thin film transistor that acts as a switching device. A gate terminal of the thin film transistor is connected to any one of the gate lines, thereby allowing a pixel voltage signal to be applied to pixel electrodes in each line.
The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a controller for controlling the gate and data drivers, and a power supply for providing several driving voltages used by the liquid crystal display device. The controller controls the timings of the gate and data drivers and further provides the data driver with a pixel data signal. The power supply uses an input voltage (i.e., an external voltage) and produces the plurality of driving voltages, e.g., common voltage(VCOM), high level gate voltage(VGH), low level gate voltage(VGL), etc., used by the liquid crystal display. The gate driver sequentially supplies the gate lines with scanning signals to drive the liquid crystal cells on the gate lines are driven one line at a time. When the scanning signal is applied to any one of the gate lines, a pixel voltage signal, supplied by the data driver, is applied to each of the data lines. Accordingly, the pixel voltage signal creates an electric field between the pixel and common electrodes, wherein the pixel and common electrodes in each liquid crystal cell thereby adjust the light transmissivity characteristics of the liquid crystal material to display a picture.
Typically, the gate and data drivers are integrated within an Integrated Circuit(hereinafter referred to as IC) chip and are connected directly to the liquid crystal panel. In connecting the gate and data drivers to the liquid crystal panel, data and gate driver IC chips are mounted onto a Tape Carrier Package (hereinafter referred to as TCP) in a Tape Automated Bonding(hereinafter referred to as TAB) process or are directly mounted onto the liquid crystal panel in a Chip On Glass (hereinafter referred to as COG) process.
FIG. 1 illustrates a schematic view of driver IC chips connected to the liquid crystal panel using a TAB process.
Generally referring to FIG. 1, the driving IC chips are connected to the liquid crystal panel via the TCP using a TAB process. Driver IC chips receive controlling signals and the direct current voltages from signal lines on a Printed Circuit Board (PCB) connected with the TCP.
More specifically, data driver IC chips 8 are connected in series to signal lines on a data PCB 6 and commonly receive controlling signals and the pixel data signal from the controller and the driving voltage from the power supply. A data TCP 10, on which the data driver IC chips 8 are mounted, connects the liquid crystal panel 2 and the data PCB 6. The data PCB 6 is electrically connected to a gate PCB 4 by the FPC 16.
Gate driver IC chips 12 are connected in series to signal lines on the gate PCB 4 and commonly receive controlling signals from the controller and the driving voltages from the power supply. A gate TCP 14, on which the gate driver IC chips 12 are mounted, is connected the gate PCB 4 and the liquid crystal panel 2.
FIG. 2 illustrates a schematic view of driver IC chips mounted onto the liquid crystal panel using the COG process.
Referring to FIG. 2, in the COG process, gate driver IC chips 12 are mounted onto pad areas of the liquid crystal panel 2 and data driver IC chips 8 are mounted on a data TCP 10 and electrically connected to the liquid crystal panel 2.
Data driver IC chips 8, mounted on the data TCP 10, are electrically connected to the data lines on the liquid crystal panel 2 and the data PCB 6. A controller 20 formed in the data PCB 6 inputs external video data and synchronized signals and generates the controlling signals and video data required by the data and gate driver IC chips 8 and 12, respectively.
The gate driver IC chips 12 are arranged on the pad area of the liquid crystal panel 2. The controlling signals and the driving voltages required by the gate driver IC 12 are generated in the controller 20 and power supply, respectively, and are supplied to the gate driver IC chips 12 via the data TCP 10 and the common lines (VL).
Gate driving signals applied to the gate driver IC chips 12 are routed through the data PCB 6, the data TCP 10 and the gate PCB 4. Accordingly, the COG process connects the gate PCB 4 to the liquid crystal panel using an Anisotropic Conductive Film (ACF) bonding process. A disadvantage inherent in ACF bonding processes lies in the fact that alien materials acting as pollutants may be present at the bonding interface.
In order to overcome the aforementioned disadvantage, liquid crystal displays employing COG processes may directly apply gate driving signals to the gate driver IC chips 12 mounted on the liquid crystal panel 2 via the data TCP 10, as shown in FIG. 3.
Referring to FIG. 3, gate driving signals required by the gate driver IC chips 12 are generated in the controller and the power supply and are applied to the gate driver IC chips 12 via the data TCP 10 and the common lines (VL). Accordingly, gate driving signals are directly transferred from the data TCP 10 to the gate driver IC 12 without passing through the gate PCB. Accordingly, the introduction of alien material at the bonding interface is eliminated because the ACF bonding process is eliminated.
However, LCD devices fabricated using COG methods have an additional problem wherein the gate driving signal, applied from one gate driver IC to the next gate driver IC, is doubly inputted and outputted in the same gate driver IC 12.